Solved! Thank you. I knew that I wanted the UID in the object's class, I just wasn't sure what to do in the event sheet to get it. I tried:

Event On mouse - On turret Clicked

Action on turret - ???

There was no option to get the ID of the turret when you are in the action menu for the turret, one needs to just select whatever variable you want and set it's value to Turret.UID, that didn't really make intuitive sense because just turret feels like it refers to the class as a whole and not the selected instance.

Picking - conditions pick, or "filter" instances. When your specify on object clicked, only the one that was clicked is applicable to the actions, thus allowing you to get that one UID. If you didn't narrow down to only one instance, it wouldn't work right. Therefore watch out for situations where you might click two of the same overlapping object - you would only get the UID of one of them. To fix that, you would need an additional condition to figure out which one you wanted (pick by z order to get the one on top is one solution).